...and this is not the only case when url_for() raising exception

render :stream => true or class method
stream effect is same

unicorn config line

listen :tcp_nopush => false

stack trace

ActionView::Template::Error (No route matches {}):

11:             <ul class="additional_locales">
12:                 <% Language.active.reject {|l| l.code == I18n.locale.to_s }.each do |lang| %>
13:                     <li>
14:                         <%= link_to url_for( :host => lang.code + '.' + request.host_with_port ) do %>
15:                       <%= image_tag("/images/flags/png/#{lang.code}.png") %>    
16:                             <%=raw lang.name %>
17:                     <% end %>

/Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/route_set.rb:464:in raise_routing_error' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/route_set.rb:460:inrescue in generate' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/route_set.rb:452:in generate' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/route_set.rb:493:ingenerate' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/route_set.rb:518:in url_for' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_dispatch/routing/url_for.rb:143:inurl_for' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/helpers/url_helper.rb:107:in url_for' /Users/andriytyurnikov/Code/futubox/app/views/shared/_nav.html.erb:14:inblock in app_views_sharednav_html_erb3474679066074452885_2165049460' /Users/andriytyurnikov/Code/futubox/app/views/shared/nav.html.erb:12:in each' /Users/andriytyurnikov/Code/futubox/app/views/shared/_nav.html.erb:12:in_app_views_sharednav_html_erb3474679066074452885_2165049460' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/template.rb:144:in block in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/activesupport/lib/active_support/notifications.rb:57:ininstrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/template.rb:142:in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/partial_renderer.rb:265:inrender_partial' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/partial_renderer.rb:237:in block (2 levels) in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/abstract_renderer.rb:33:inblock in instrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/activesupport/lib/active_support/notifications.rb:55:in block in instrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/activesupport/lib/active_support/notifications/instrumenter.rb:21:ininstrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/activesupport/lib/active_support/notifications.rb:55:in instrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/abstract_renderer.rb:33:ininstrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/partial_renderer.rb:236:in block in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/abstract_renderer.rb:22:inwrap_formats' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/partial_renderer.rb:228:in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/renderer.rb:41:inrender_partial' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/renderer.rb:15:in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/helpers/rendering_helper.rb:24:inrender' /Users/andriytyurnikov/Code/futubox/app/views/layouts/application.html.erb:17:in _app_views_layouts_application_html_erb___3265135085123127531_2169541100' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/template.rb:144:inblock in render' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/activesupport/lib/active_support/notifications.rb:57:in instrument' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/template.rb:142:inrender' /Users/andriytyurnikov/.rvm/gems/ruby-1.9.2-p180/bundler/gems/rails-505defc27ead/actionpack/lib/action_view/renderer/streaming_template_renderer.rb:73:in `block (2 levels) in delayed_render'